This invention relates to the process of installing at least one roof mounted oxygen-fuel burner in a glass melting furnace. More particularly the invention relates to the process which includes the preparation of the furnace refractory roof to accept the roof-mounted oxygen fuel burner, and the preparation and conditioning of the refractory ceramic burner block, followed by its installation.
With the exception of cold top electric furnaces, glass melting furnaces typically have a refractory roof, commonly known as the crown. The selection of refractory materials for the crown is governed by the type of glass being manufactured, and specifically the ability of the refractory i) to withstand the glass melting temperature requirements and ii) to resist volatile species liberated in the glass melting process.
Conventionally, glass furnaces have not been equipped with burners built into the crown of the furnace. Glass batch materials have traditionally been melted using one, or a combination of, electrodes or flames that are generated substantially horizontally with respect to the surface of the glass batch materials, from burners mounted in the furnace walls, or associated with regenerative air ports.
Recently, it has been proposed to install roof-mounted gas burners, such as oxygen-fuel burners, in refractory lined glass melters. These burners are directed downwards at an angle greater than 45xc2x0 with respect to the surface of the glass forming material, and are controlled such that a generally columnar fuel and oxygen flow combusts proximate to the top surface of the glass forming material, to produce a flame that impinges the surface of the raw glass forming material. This permits a significant increase in heat transfer into the glass, while maintaining refractory temperatures within safe operating limits, and avoiding the overheating of the roof and walls of the furnace. This technology approach is described in U.S. Ser. No. 08/992,136, now U.S. Pat. No. 6,237,369 (corresponding to PCT Publication WO 99/31021) and U.S. Ser. No. 9/374,921, both of which are incorporated herein by reference as if fully written out below.
When roof mounted burners are installed in a new furnace before initial firing, the characteristics of the furnace refractory can sometimes be accommodated by the burner block to be provided. In other instances, incompatibilities of the materials of the furnace refractory and the burner block must be taken into account. This is a particular problem in retrofit installations, where at least one roof mounted burner is to be installed in an existing furnace structure.
Because of the high operating temperatures in the furnace crown and the potentially high temperature of the oxygen-fuel flame, the selection of the burner block refractory material is critical. In certain conditions, there may be material incompatibilities between the burner block materials and the crown materials which necessitates a barrier between the two materials. Representative ceramic materials that are utilized in either the furnace refractory or the burner blocks are silica, alumina zirconia silicate (AZS), zirconia, zircon (zirconia silicate), and fused cast alumina refractories.
Retrofit installations involve drilling the crown either hot or cold depending upon the furnace status. If a new furnace or new crown section is prepared while the furnace is cold, there is the opportunity to either drill a hole or install a prepared section with the hole pre-drilled or cast. When the burner is installed in a hot furnace which is already in operation, there is a requirement to minimise the risk of thermal shock. In any circumstance, due to risk of damage to the refractory materials in the crown, the exterior surface of the crown must be prepared to enable a gas tight seal when the burner block is installed.
The present invention is directed to a process for installing at least one oxygen-fuel burner in the crown of glass melting furnaces having various refractory constructions and utilising burner blocks of different materials in both hot and cold retrofit applications, and in new purpose built applications.
The present invention provides a process for installing a refractory burner block in a glass furnace crown, wherein the glass, furnace crown comprises a second refractory material different than the burner block refractory, comprising:
installing a refractory crown block in the furnace crown, wherein the crown block refractory is compatible with the burner block refractory and the second refractory material, wherein the crown block is provided with a hole for accepting the burner block; and
disposing the burner block into the crown block hole in sealing engagement therewith.
Optionally, the crown block has a greater overall depth than the furnace crown refractory.
The present invention further provides a process for installing a refractory burner block in a hot glass furnace crown, wherein the glass furnace crown comprises a second refractory material different than the burner block refractory, comprising:
removing crown insulation from the exterior of the furnace crown;
inserting a patch of refractory material compatible with the furnace crown second refractory material into the crown in the vicinity of the removed insulation;
drilling a hole into the crown through the refractory patch, optionally with a water cooled diamond drill; and,
inserting the refractory burner block into the hole in the furnace crown through the refractory patch.
In one embodiment, wherein the burner block refractory is incompatible with the furnace crown second refractory material, the process includes applying a chemical barrier to the external surfaces of the burner block refractory, which chemical barrier is chemically compatible with the furnace crown second refractory material, prior to insertion in the furnace crown.
In another embodiment, the present invention provides a process for installing a refractory burner block in a glass furnace crown, wherein the glass furnace crown comprises a refractory material, comprising:
installing an insulating barrier mounting block on the upper surface of the furnace crown, wherein the mounting block is compatible with the burner block refractory and the refractory material, wherein the mounting block is provided with a hole for accepting the burner block, and wherein the insulating barrier is prepared when the furnace crown is not hot; and,
disposing the burner block into the mounting block hole in sealing engagement therewith.
This embodiment is preferably utilized when the furnace crown refractory material is a highly thermally conductive fused cast refractory material.
In a further embodiment, the present invention provides a process for installing an externally staged oxygen-fuel burner in a glass furnace crown, comprising:
drilling in the furnace crown, at least a first hole for accepting a burner block and at least a second hole for accepting at least one externally staged oxygen injector means;
positioning a first transition block spacer over the first hole, said first transition block spacer being provided with a burner block hole for accepting the burner block in communication with the first hole;
positioning one of the first transition block spacer and an optional at least second transition block spacer over the at least second hole, said first or at least second transition block spacer being provided with at least one oxygen injector hole for accepting the oxygen injector means in communication with the at least second hole,
inserting the burner block through the first transition block spacer into the first hole in sealing engagement;
inserting an externally staged oxygen injector means through at least one of said first and second transition block spacer into the at least second hole in sealing engagement; and
applying a castable material to seal the first and optional second transition block spacer.